Abstract
We report results concerning the functionalization of graphene-based nanoplatelets for improving the thermal energy storage capacity of commonly used phase change materials (PCMs). The goal of this study was to enhance the low thermal conductivity of the PCMs, while preserving their specific and latent heats. We focused on wax-based PCMs, and we tested several types of graphene nanoparticles (GNPs) at a set of different concentrations. Both the size and shape of the GNPs were found to be important factors affecting the PCM’s thermal properties. These were evaluated using differential scanning calorimetry measurements and a modified enthalpy-based water bath method. We found that a small addition of GNPs (1% weight) with high aspect ratio is sufficient to double the thermal conductivity of several widely used PCMs. Our results suggest a simple and efficient procedure for improving the thermal properties of PCMs used in thermal energy storage applications.
Highlights
Academic Editor: Andrea FrazzicaCommon heat transfer fluids (HTF), such as water, oil, and ethylene glycol solutions, have comparatively low heat transfer rates, implying low efficiency and large structures, that affect both the manufacturing and operating costs
We found that thermal conductivity was enhanced at even lower mass fractions with the addition of a 0.01 mass fraction to nanoplatelets with 15 μm diameters
(Lansing, nanoplatelets are ultrathin of graphite beginning at Michigan, a few nanometers and diameters ranging up fromparticles a few microns
Summary
Common heat transfer fluids (HTF), such as water, oil, and ethylene glycol solutions, have comparatively low heat transfer rates, implying low efficiency and large structures, that affect both the manufacturing and operating costs. 15 μm, a thickness of less than 10 nm, and BET surface area of around 30 m2 /g, when mixed with paraffin (n-docosane, with melting temperature 53–57 ◦ C) with a mass fraction up to 0.07 xGnP-15, linearly increased the thermal conductivity to a value of 0.8 W/mK They reported negligible changes in the latent heat fusion with the addition of up to a 0.07 mass fraction of graphite nanoplatelets. We chose to work with exfoliated expanded graphite nanoplatelets of differing sizes, aspect ratios, and surface areas that were similar in concept to those used by Drzal et al The nanoplatelets had in-plane and out-of-plane thermal conductivities of 3000 and 6 W/mK, respectively They were chosen because of their superior thermal conductivity compared to that of carbon nanotubes and their reduced cost. Some preliminary efforts were undertaken to compare our findings in thermal
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